Plus, Trump reveals his strategy to win the presidency. Is it a winning plan?

And Trump and Sanders challenging each other to a debate. Tonight, Trump gives his final answer.

Good evening, I'm Jim Sciutto in again tonight for Erin Burnett. And OUTFRONT tonight, breaking news, protesters gathering right now outside a Donald Trump rally in California. Trump protesters squaring off with Trump supporters. Police estimate as many as 1,000 people on hand. Police deployed in riot gear, concerned about the possibility of violence. And there is Trump inside the convention hall, we're learning of Trump's strategy to fight Hillary Clinton in the general election, a strategy that includes challenging her in California. A state that hasn't voted for a Republican president since 1988. Trump claims this year will be different.

(BEGIN VIDEO CLIP)

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: No other Republican -- let's say Ted Cruz won or let's say anyone of them won. They wouldn't even come here for dinner. Because they are told that as a Republican, you have zero chance, okay? I really believe we're going to win it. I think we have a real chance to win it. And you know what, I view it strategically also. Because if we don't win it, they are going to spend one hell of a fortune in fighting me off, that I can tell you.

(END VIDEO CLIP)

SCIUTTO: Sara Murray is OUTFRONT tonight in San Diego. So, Sara, on the protests first, they have been gathering there for hours now. More than 1,000. I mean, those are big numbers.

SARA MURRAY, CNN POLITICS REPORTER: They are big numbers, Jim. And for a lot of the day, it was relatively nonviolent. They had protesters out there, they were singing, they were dancing, they were chanting. But there was a tense moment when protesters tried to breach a police barricade and we saw them interacting with the police. At that point, the police were trying to push them back. And the San Diego Police Department has tweeted there has been one arrest, and our producers and reporters outside did see one protester taken away in handcuffs.

And this tends to be a more tense moment right now, Jim, because you have the Donald Trump fans who were leaving this event. We're going to be passing the protesters, and the police are taking pains to ensure there is a large buffer between the protesters and those Trump supporters who are exiting. Obviously, they want to avoid any conflicts they can.

SCIUTTO: We're seeing some of them waving a Mexican flag there. Also, what are the political strategy now? Trump says he can put California in play in a general election. And we know that's a tall order. Is that realistic, or is this about making the Democrats spend money there?

MURRAY: Well, a tall order seems like an understatement, Jim. Donald Trump did float with the idea that if he can just get Democrats to spend money in California, maybe that would be a victory for him. But as for actually winning the state, like you said, no Republican has won California since 1988. This is a state that President Obama won by more than 20 points. And it's a kind of state where if you were playing to win, you would need to put some kind of infrastructure in place. And that's one thing we have not seen from the Trump campaign, even though Donald Trump has said he's going to put 15 different states in play, he's going to play in places that Republicans have not played in the past.

What we have seen is, he doesn't even really have a robust staff presence in some of these traditional battleground states. Places like Ohio, places like Florida. Places where you would expect a campaign to be building out, the Trump campaign is really lagged behind on that front. So they're really going to have to get up to speed and build out far beyond that if they're helping to play ball in states that Democrats have won for many, many years -- Jim.

SCIUTTO: All right. Sara Murray tonight in California. Well, California just one of the states on Trump's proposed victory map.

(BEGIN VIDEO CLIP)

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: What I'm going to do is, I want to focus on 15 or so because we have to win. And I want my energy to be put in the states where it could go either way.

(END VIDEO CLIP)

SCIUTTO: Tom Foreman is OUTFRONT tonight. So, Tom, how does the Trump campaign say they're going to make this strategy work in the general?

TOM FOREMAN, CNN CORRESPONDENT: Well, as Sara hinted, Jim, probably not on the West Coast. If you think about it, Washington, Oregon, California, have all reliably voted Democrat since the early 1990s. And look at the overall map here, as the polls and past performance suggests it's going to be. You see a lot of red out there for the Republicans, some blue for the Democrats. Yellow for the battleground states. The Democrats mathematically have an advantage, because a lot of these blue states have very big populations, lots of electoral votes.

So when he talks about these 15, what is he talking about? Well, he could very well be talking about these states based on his comments. And here's an example. Let's talk about New Mexico, for example. This is right down here, on the border. It's one that he has been talking about for some time. And that's why he thinks it might have some traction for him. He thinks it stands on the border, could assure people there that they're going to somehow cut down on drug traffic, they're going to cut down on job loss. They're going to feel more secure.

[19:05:12] So he thinks that might give him traction. You might tilt the state between going blue back to the red column. Let's go up toward the Rust Belt. And we're going to define the Rust Belt in a very broad sense, all the way from the Midwest over here to the East Coast. Basically, every place where there has been a strong blue collar presence in that general region there. He thinks he has a chance up here, because first of all, as you'll note, there are several yellow battleground states in there that he can tie together. Secondly, he thinks even in some of the blue states, there could be trade deal backlash. Clinton up there who feel that Hillary Clinton was tied to trade deals that they think sent their jobs overseas.

And lastly, it doesn't hurt him that his home state of New York will not really part of the Rust Belt, is at least sort of tied to it, and could help knit all of this together in a confederacy that might help him with all of his votes up there. This is the thing, though. Stringing all of this together, Jim, seems like a fine idea if you're hoping to win that way. But that strategy can count both ways. For example, Hillary Clinton could hit him in Georgia down here. Which has been a red state that has shown some signs of maybe tipping some.

She could hit him over here in Arizona and that would force him to defend places that right now he may not think he has to. It's going to get very complicate and the chess moves will be all over the place, Jim.

SCIUTTO: No question. Tom Foreman, thanks very much.

We have a great panel OUTFRONT tonight. Hillary Clinton supporter, Bernard Whitman. Bernie Sanders support Sally Kohn. The co-chair of Donald Trump's campaign here in New York Joseph Borelli. Former RNC Communications Director Doug Heye. And Donald Trump supporter Erin Elmore as well as TheBlaze's Buck Sexton.

Doug, if I could begin with you first, if you look at these 50 states strategy as explain there so well by Tom Foreman. Can he really change the map?

DOUG HEYE, FORMER COMMUNICATIONS DIRECTOR, REPUBLICAN NATIONAL COMMITTEE: Maybe in some places he can change the map. But California is not where it starts. I worked at the California Congressional delegations for six and a half years. Ran a race out there, worked on others. He's got some challenges there and some challenges that aren't just Trump's challenges. It's where do you win, what counties are you driving up the vote? Is that in the central valley, are you trying to do so in San Diego? And then how? What strategy are you using? And some of this is what Sara talked about. And then with who? It's a weak state party. The conservative activists have fallen in recent years. There is not a lot there to build for Trump to really get there.

SCIUTTO: Joe, you heard Sara Murray talking about the organization that he lacks in these states. How can he pull off this strategy if he doesn't have the staff on the ground?

JOSEPH BORELLI, NEW YORK CO-CHAIR, DONALD TRUMP CAMPAIGN: Well, I think a big picture is that he's trying to flip the script. Someone that has done more with less both, less money spent, less staff. And we see him winning, you know, in a lot of states in the primary. Essentially, this puts Hillary Clinton on the defensive. She is someone that never expected to have to even consider defending California. A big state, a lot of electoral votes. Now with just some rallies, with just some earned social media, with some earned regular media, he could potentially just challenge her. They are enough where it makes a debt in her budget.

SCIUTTO: Buck, do you buy that?

BUCK SEXTON, HOST, THEBLAZE'S BUCK SEXTON SHOW: Look, I think that Trump has been able to do a lot of things that everybody thought he couldn't. I think that going after new york and going after California are more a rhetorical play than a play to actually win those states. Because it is just a way of him saying, look, we're going after everything, we're changing the entire narrative here, and I don't think he's going to win either of those states. But I do think that in places like Michigan, Wisconsin, places where he will be competitive or at least it looks like he'll be competitive, saying that he's going after Democrats on their home turf plays into the Trump narrative, which is I'm just a lean, mean, winning machine and that's essentially what he's trying to get across.

SCIUTTO: Bernard, does the Clinton campaign look at this and get worried?

BERNARD WHITMAN, DEMOCRATIC STRATEGIST: No, I don't think so at all. This is a classic fake. I mean, I think that Donald Trump would stretch himself so thin that he would actually crack. The idea that he could put California and New York in play is absurd. In fact, I think there's a lot more concern about his winning Arizona and Georgia, and if I were advising him, I would say, spend your time in Michigan and Ohio and Pennsylvania and Wisconsin. He's got to win single state that Mitt Romney won or John McCain won, plus some. Don't forget, these guys both lost. Currently he's underperforming. Both of those guys among Whites, among Hispanics, among women. He's got a tall order cut out for him. So, I think this is braggadocios at its best which is the fine point of Donald Trump.

SCIUTTO: I see you nodding your head, Sally and smiling a little bit.

SALLY KOHN, CNN POLITICS COMMENTATOR: I mean, yes. Look, and I am -- I am constantly pointing out to certainly my side, you know, of the Democratic left and America that Donald Trump can win, it is possible. We shouldn't sort of rest on our laurels. But, yes. This is sort of classic Trump. And -- we all know whomever the nominee is on the Democratic side versus Trump, this is going to play out in the Rust Belt, you know, in four states. That's what it's going to all come down to. Which, by the way, is a travesty that American politics and elections always come down to just a few states mattering more than the rest. But there you have it. The rest is just talk.

SCIUTTO: So, Erin, I want to ask you, as we've been talking here, we're still seeing those pictures, these enormous protester presence outside the Donald Trump rally. I just want to play some sound of both Trump and Sanders, what they have said at events when violence has happened. Let's have a listen.

TRUMP: The guards are very gentle with him. He's walking out like a big high fives, smiling laughing. I would like to punch him in the face.

SANDERS: We need a political revolution where millions of people stand up, fight back, and create a government that works for all of us.

TRUMP: So I was rough with him. And I started screaming. I said, you know, get the hell out of here!

(END VIDEO CLIP)

SCIUTTO: Erin, is Donald Trump partly to blame for the kind of violence we have seen outside his rallies?

ERIN ELMORE, DONALD TRUMP SUPPORTER: Certainly not. He's not inciting violence. And these are certain, you know, little, you know, little tidbits of information taken out of context, as well. I think Bernie is just as responsible saying we need to spark a revolution. So I think these are Bernie's people, they are getting out there, sort of the occupy Wall Street movement, getting aggressive.

SCIUTTO: I want to get to you, Sally.

HEYE: If Bernie Sanders is just as responsible, you're admitting that Donald Trump is also partially responsible. Look, anybody who is setting fires or throwing rocks at police should be thrown in jail. But when we have candidates who are saying, punch somebody, I'll pay your legal bills or welcome to the revolution, you were contributing to this atmosphere of ugliness.

campaign is based on an opposition to the sort of hawkish pro-war sort of -- it is a pacifist driven movement. He has very clearly denounced violence. Anytime that has come. Anywhere near his campaign. And to say revolution, come on. Then everyone that Tea Party has been inciting violence too.

(CROSSTALK)

But let's be clear. Donald Trump has encouraged and incited people to actually be violent by saying, I want to punch him in the face myself and I'll pay your legal fees and his rhetoric throughout this campaign has been based on violence against Mexicans and Muslims and it's just like --

(TALKING OVER EACH OTHER)

SEXTON: Sanders is not responsible for the violence of the people that are protesting in his name. It is interesting though that these elements of the left like to show up in places and break stuff and wave Mexican flags. When you look and see what the American left has devolved into, you have a lot of people that act in this hysterical fashion. I don't blame Bernie, I just blame the people that think Bernie is actually going to create a political revolution. It's ridiculous.

KOHN: There are 1,000 people in San Diego.

BORELLI: Democrats saying that these are just a few rotten tomatoes in the crowd when one nut job at a Trump rally punches someone, media head exploded.

WHITMAN: That was Donald Trump from the stage -- to punch protesters in the face.

(TALKING OVER EACH OTHER)

Bernie's condemnation in Vegas --

SCIUTTO: We'll have to leave it there. Thankfully there will be no punches here, at least tonight. No punches tonight. Thanks very much. My panel. We're going to have them back.

OUTFRONT next, he once called Donald Trump a dangerous conman. So why is Marco Rubio now saying his former rival should be president?

And we will continue to follow the protest as well outside that Trump rally. We'll take you there, live.

(COMMERCIAL BREAK)

[19:17:07] SCIUTTO: Breaking news. You're looking at live pictures of protesters gathering outside of Donald Trump's rally in San Diego. This is happening as we speak there. Police say protesters tried to breach a secured area and at least one arrest has been made so far.

Our Paul Vercammen is there now. Paul, is the situation deteriorating?

PAUL VERCAMMEN, CNN CORRESPONDENT: Well, just seconds ago, the San Diego Police Department in riot gear make a major move. And what they did is, they separate the people who are with me in the area I'm standing in. These are anti-Trump demonstrators. And if you look across the street, those are all Trump supporters. They were yelling "USA, USA," they were shouting, they were getting into this with each other. They're yelling all sorts of different things. And as we said, there have been some arrests. I don't know if they're detaining this person, because this is a clear arrest -- just getting to the other side. They let him go.

They're trying to separate the Trump supporters from the anti-Trump demonstrators. And they had made some major moves with barricades and with police in riot gear. And at some point, they were separated by hundreds of yards. But as they came out of the center on the streets of San Diego, where right outside the historic Gaslamp district, that's where we had the standoff, the shouting -- the skirmishes between both sides. And they have been yelling at each other. We saw some punches thrown, two or three. But basically, we have not seen a large amount of arrests, just all the shouting going on right now.

SCIUTTO: Thanks very much, our Paul Vercammen who is there live in San Diego. You're seeing him there in the midst of what are becoming violent protests there, potentially violent protests. As you're watching this, Doug, formerly with the RNC, we'll basically seeing this as every event now.

HEYE: We're seeing this at every event. We're hearing the words, as Paul just said, punches thrown. It doesn't matter how many punches were thrown. Punches are thrown, we're seeing this time after time. And it's why the committee is so concerned about what we're going to see in Philadelphia, as well. This is happening on both sides. There is a lot of anger on both sides, they deserves to be a lot of anger at Washington from both sides. But it's why both committees are scared about some of the security procedures that we'll see at the convention.

SCIUTTO: Erin, I have to ask you, does this damage Trump as a candidate? If he -- if people see consistently that he engenders this kind of response from people?

ELMORE: We already know that nothing the Donald Trump does or anything around him causes any sort of change. I've always called him the Teflon don and that's absolutely true. No matter what he says or what he does, his voters are still coming out and right now he and Hillary, they're neck and neck. So nothing really matters.

SCIUTTO: Well, let's be frank, in the primary process, where different set of voters. As we get into the general, Sally, Bernard? Do you think that --

WHITMAN: But it does matter. This is absolutely outrageous. And Donald Trump needs to get out there and say, you know what, peaceful protests are absolutely fine. There is nothing wrong with that. I totally respect people's right to protest together, to voice their opinions. But my supporters should calm down, be civil, respect one another. But you know what, we're never going to hear that because that is not in his interest.

(TALKING OVER EACH OTHER)

KOHN: Oh, my gosh, it turns out -- that's so interesting. You're saying the punches were thrown but you're going to assume which side they're from. Listen, I misrepresent -- I really resent the mischaracterization of this. Again, we have so far heard 1,000 of people there protesting peacefully all day. One arrest and violence may be happening in a moment. And let's be clear --

(TALKING OVER EACH OTHER)

SCIUTTO: The police have to separate them. The police have to separate them.

KOHN: And that's -- but them, both sides. And by the way, we in the media really love when this stuff gets ugly. Because we want to cover it more. The fact that people are out there, exercising their civil and constitutional right to object is important and significant. God bless them all. I hope that the protesters on both sides stay peaceful. But yes, this is important. People need to see this. If Trump is sucking up all the media oxygen, this is the only way for these people to be heard.

SCIUTTO: Joseph, I have to ask you. I saw Donald Trump at a rally two days ago when someone was removed, a protester was removed, and he said don't hurt him and then he made a comment saying, well, I just say that for the television cameras. Kind of --

BORELLI: Well, I think the media always overplays whatever he says. But --

SCIUTTO: I'm quoting the candidate here.

BORELLI: Let's remember what went on outside that rally where you had shamefully so many protesters from the Left, assaulting police officers, throwing bottles, throwing rocks. Honestly, if they were my supporters, I would be ashamed of myself. And I think they have to own it.

KOHN: They -- are they wearing Bernie Sanders t-shirts?

SEXTON: This is a distinction that I think should be made. Yes, I would like it too, honestly, if Trump would come out and say, look, everybody behave. If you're on my side, behave. And I think he started to do that, he should do more of that. But on the left, you see people that actually think that they have the hackers veto, that they should be able to shut down Trump rallies. They absolutely think that it's their right to say that Trump is beyond the pale. Look, he is the nominee for the GOP. We all know -- [19:22:10] SCIUTTO: Why is it -- is it too much to ask, Doug, for the

presumptive GOP nominee to make a statement, saying, I don't want to see violence?

HEYE: Absolutely. It should be common sense for him to do it. It should be common sense for Bernie Sanders to be more declarative than he was after the obviously disgrace that we saw in Nevada. No hands are really clean here. It's a disgrace and we should do what he's

(TALKING OVER EACH OTHER)

WHITMAN: Why is Donald Trump responsible at all for people protesting his rallies?

KOHN: Because he has incited it and encouraged it.

WHITMAN: He is a candidate for office, expressing his views and you may not like it --

(TALKING OVER EACH OTHER)

KOHN: You know what? You know what? I'm sorry, but the list of things I have to talk to my seven-year-old about to not emulate in the potential possible future president of this country is getting a little too long. You want to draw analogies between the protests and Trump, fine, you're free to do that. But they're not running to be president, he is. And he is responsible to do, stop stoking this kind of violence and hatred in this country.

SCIUTTO: Erin.

ELMORE: I can control my three-year-old. How do we expect Donald Trump to control adults by the millions?

KOHN: I want him to control himself and be a better role model if he wants to run this country.

ELMORE: How if he's going to be --

(TALKING OVER EACH OTHER)

It's not just going to happen. He isn't capable - of telling people how to act and making them act.

WHITMAN: But when you start to become violent, that's when the leaders of the two parties have to come out and say, you know what, this is unacceptable. We need to have civil discourse, you need to be able to express yourself freely. But when it comes to shutting people down, or even worse, throwing punches, that is absolutely unacceptable.

SCIUTTO: You're saying both parties have a responsibility.

WHITMAN: Both parties have a responsibility. I was actually incredibly frustrated with Bernie Sanders. I think he really lost a lot of respect and a lot of support from people that have said, you know what, he's basically a good guy. He actually waffled on coming down hard, on the Vegas --

KOHN: And I said as much too by the way.

SEXTON: Democrats are the ones that have actually had protest moments or people that support the Democratic Party, the ones that are engaged in protest movements where the media has to say, well, it's mostly peaceful, except for people burning down, except for people burning down buildings or people who are throwing rocks at police or people who are doing other things that are violent and illegal. Those are always people --

SCIUTTO: I do want to ask this though. I wonder, is that anger that we see out on the streets that these are again live pictures here. Does that reflect just the broader state of mind right now of voters on both sides?

WHITMAN: When Donald Trump began his campaign by suggesting that Mexicans are all rapists and murders, what do you expect supporters to do? Go out and take matters into their own hands. That's what my concern is, and when you couple that with his support for allowing people to carry guns in churches and colleges and office buildings and restaurants. I mean, my God. That's absurd. That's absurd.

KOHN: This is not -- this is not a civil candidate. His discourse, his message, what he wants to do to massive parts of this country is not civil. I would like to see the protesters to be honest, be infinitely more peaceful because I think their greatest power is in contrast to his hateful rhetoric and the violence that we have seen, some of his supporters --

SCIUTTO: Folks, great discussion on that. Again, we're going to keep you around. Thanks very much. And just a reminder to our viewers, we're showing live pictures there of protests outside a Trump rally in San Diego and a huge police presence. We're going to stay on top of this.

OUTFRONT next, a Trump/Sanders debate. Ahead, what Donald Trump is saying about that tonight?

And new details in the search for the missing EgyptAir Flight 804. Tonight investigators zeroing in on what they believe could be the plane's location.

(COMMERCIAL BREAK)

[19:29:20] SCIUTTO: Tonight, Donald Trump changes his mind again, moments ago, Donald Trump declaring that he will not debate Bernie Sanders just hours after he had insisted that he would love to do so. In a statement, Trump said it would be, quote, "inappropriate, since Sanders is running second behind Hillary Clinton."

Sanders had this message for Trump.

(BEGIN VIDEO CLIP)

SANDERS: You know, I hope that he changes his mind again. I mean, Mr. Trump is known to change his mind many times in a day. And I would, you know -- Trump goes around and he's a bully. He's a big, tough guy. Well, Mr. Trump, what are you afraid of? Why do you not want to see a debate here in California and obviously all across this country?

(END VIDEO CLIP)

[19:30:00] SCIUTTO: Is the back and forth between Trump and Sanders leaving Hillary Clinton high and dry?

SEN. BERNIE SANDERS (I-VT), DEMOCRATIC PRESIDENTIAL CANDIDATE: We can win here in California. And we can come out with the Democratic nomination.

MCLEAN: As new poll numbers show Clinton and Sanders now in a dead heat in California, Sanders continues to make the case that he has a better shot of winning in November.

SANDERS: If we win the Democratic nomination, we're going to defeat Donald Trump, not only are we going to defeat him, we're going to defeat him very badly.

MCLEAN: Clinton continues fighting for votes in California. Today speaking to community leaders in Oakland, and hitting the airwaves with ads in English and Spanish.

While hitting Trump at rallies.

HILLARY CLINTON (D), PRESIDENTIAL CANDIDATE: Send a message to a demagogic, rhetorically divisive and dangerous candidate that when you think about the future, you don't see Donald Trump's face up there.

MCLEAN: On the verge of clinching the nomination, Hillary Clinton trying to shift her focus to the general election.

CLINTON: Donald Trump is an unqualified loose cannon who cannot get near the most powerful job in the world.

MCLEAN: But Sanders is not making that easy. On Jimmy Kimmel last night, Sanders called out Clinton's comments to CNN earlier this month that she had the nomination wrapped up.

SANDERS: Just arrogance. I think on June 7th, people of California will have a message for Secretary Clinton.

MCLEAN: Clinton has declined to debate Sanders in California, so instead he's challenged Trump. Sanders said two networks offered to host the debate but today, Trump backed out, saying in a statement, "As much as I want to debate Bernie Sanders, and it would be an easy payday, I will wait to debate the first-place finisher in the Democratic Party. Probably crooked Hillary Clinton or whoever it may be."

SANDERS: I hope he changes his might be again. Mr. Trump is known to change his mind many times in a day. And I would, you know -- Trump goes around and he's a bully. He's a big, tough guy. Well, Mr. Trump, what are you afraid of?

(END VIDEOTAPE)

MCLEAN: And this afternoon, Sanders sent out another statement about this debate proposal, saying he hopes Trump will change his mind. Now, while Bernie Sanders doesn't want to let this idea go, a lot of Democrats wish that he would. In fact, West Virginia Senator Joe Manchin called it B.S. that Sanders continues to push this debate -- Jim.

Compared to eight years ago, against Barack Obama, that race was razor-thin. I mean, yes, California and New Mexico, New Jersey should actually vote. The contest is over and he should exit the stage gracefully like Ted Cruz.

SCIUTTO: Sally, I wonder if you have a slight different opinion on that.

SALLY KOHN, CNN POLITICAL COMMENTATOR: They should vote and two candidates to choose between, it's just not over yet. And yes, I will admit, that the math looks hard for Bernie Sanders. But it is also more -- it is still telling for Hillary Clinton that at this point, she can't put it away against him.

And is by the way, still use for the Democratic process that again it is nice the Democrats are talking about substance, talking about the economy, and foreign policy, and trade policy, and having that discussion. And it is good clarifying process for America and for the future of the Democratic Party.

SCIUTTO: I have to ask you on this debate idea, which Donald Trump has put to rest today. But he had said it was a dream, it would have been a dream to debate him. Why does he turn around?

JOSEPH BORELLI, NEW YORK CO-CHAIR, DONALD TRUMP CAMPAIGN: Let's start here. Something that was started on a comedy show, Jimmy Kimmel, like Hillary Clinton saying that Beyonce was going to be her vice presidential pick. It was getting a lot of media buzz.

I don't think it would have done anything to benefit Donald Trump. And as far as Bernie Sanders goes, he should be more concerned that Hillary Clinton, who he is in a dead heat with in California, is refusing to debate him, despite promising to do so when they set out the agenda for the debates.

I want to go back to their point. Hillary Clinton seems a bit delusional now if she thinks this race is over and she's acting as though she's won the nomination race.

I actually will agree with Sally on this. Don't get too excited. She has -- he said a tinge of arrogance and he's right.

SCIUTTO: Buck, I want to talk to you, because they are obviously from different parties, Sanders and Trump. But a lot of positions we'll be talking about earlier are very similar. Just for our viewers, we're going to play a few comments back and forth.

(BEGIN VIDEO CLIPS)

SANDERS: We're not going to cut Social Security.

TRUMP: I will do everything within my power not to touch Social Security.

SANDERS: Bush's decision to get us into a war in Iraq unilaterally was one of the worst foreign policy blunders in the history of the United States.

TRUMP: Obviously, the war in Iraq was a big fat mistake.

SANDERS: We need a serious discussion about the role of superdelegates. Clearly, the current situation is undemocratic.

TRUMP: Hundreds of delegates ahead. But the system, folks, is rigged.

(END VIDEO CLIPS)

SCIUTTO: Is Trump missing an opportunity here to win over some independents?

BUCK SEXTON, HOST, THE BLAZE'S "BUCK SEXTON SHOW": Well, I think that he wants make sure everyone knows he's the front runner for the GOP. He is the come nominee, rather. And he's only going to debate whoever he has to on the Democrat side. So that's obvious.

I do think he will try as part of his strategy to win over Bernie supporters. I don't think it's absolutely baked in the cake that everybody who supports Bernie Sanders is just going to march in lockstep behind Hillary Clinton. I don't think that's necessarily going to be the case. There is some crossover between some of the Trump positions on trade

and workers and manufacturing base with Bernie Sanders. And so, it's -- he is not going to do it. He obviously -- I don't think he was ever going to do it.

But we will see this return to, can Trump pull over Democrat voters? And if he's going to do that, it's going to be people from the Bernie side, not from obviously the Hillary diehard supporters.

SCIUTTO: Erin, what's his message gong to be to those kinds of voters, to try to draw them into his camp?

ERIN ELMORE, DONALD TRUMP SUPPORTER: Anti-establishment. I am not the norm. I have completely swung the pendulum the other way, come to my side, you're going to see change.

Even now Republicans that were all the way, on the right, are really -- they have made their bed with Donald Trump. They were super religious, anti-homosexual. Instead of focusing on what the car Republicans care about.

And that is what Donald Trump is focusing on and that's why he's winning. So, those are the people that maybe Bernie can get to.

SCIUTTO: Doug, are you seeing the party step into line behind Trump now?

DOUG HEYE, CNN POLITICAL COMMENTATOR: We're starting to see more people fall into line. It seems somewhat natural. But there are two types of resistance. You see the attacks that we saw in Susana Martinez. That tells people, maybe I don't want to get on board with this right now.

And then you also see people who are starting to say, I'll support the nominee, and that's about it and they're not Never Trump, they're hesitant Trump, which means they're not going to work hard for his election.

SCIUTTO: It doesn't really work as a hashtag, though. Hesitant Trump.

HEYE: Never Hillary is a much better one.

SCIUTTO: All right. Folks, you have been great. Thanks very much.

OUTFRONT next, we're following breaking news. Protests erupting outside a Trump rally tonight. We will take you back out there, live.

Plus, new details in the search for EgyptAir Flight 804. Investigators could be one step closer to finding out what brought the plane down.

And aging, overcrowded and in need of serious upgrades. OUTFRONT tonight, an exclusive investigation into the nation's crippled airports.

(COMMERCIAL BREAK)

SCIUTTO: Breaking news, live pictures right now of protesters outside Donald Trump's rally in San Diego. The crowds growing more tense. Police now telling us at least three arrests have been made.

Our Paul Vercammen, he is still there.

Paul, what have you been seeing now?

PAUL VERCAMMEN, CNN CORRESPONDENT: Well, Jim, looking at the live pictures, you can see these demonstrators right in front of us have decided to sit down. They are anti Trump demonstrates. And if you look also, you can see all of these officers in their riot gear, some with advisers flipped up, some down. Clearly, they're getting ready to stage here because not long ago, we heard the call on the bull horn in both English and Spanish, declaring this to be an unlawful assembly. That is usually the precursor to trying -- and there are hundreds and hundreds of officers to move people out and separate the crowd.

We've seen pushing. We have seen shoving. We've seen some punches thrown. But so far, it mainly has boiled down to a shouting match.

Over here to my right, you can smell it right now. It smells like they're burning something. Most likely from these protests, possibly a Trump flag or a Trump cap or something like that, where we are right now, this is the anti-Trump crowd. They have separated, most of the Trump supporters from this crowd.

And as I said, the bull horn announcement that this is unlawful assembly. You see the officers clearly getting ready to stage something. And I would guess the next hour or so here, Jim.

Back to you.

SCIUTTO: All right. Paul Vercammen in the middle of it there. We will continue to follow the story of the protests outside the Donald Trump rally.

But also breaking tonight, the search for EgyptAir Flight 804. Officials now hiring a private company to help find the plane's crucial black boxes. Investigators in a race against time, just three weeks remain until the batteries in those black boxes run out.

Now, they're narrowing the search, focusing on a three-mile stretch in the Mediterranean, after detecting signals from the plane's emergency beacon.

David Gallo is OUTFRONT. He co-led the international effort to locate the remains of Air France Flight 447, one of the toughest searches in recent history.

So, David, it's now been eight days. Do you think they can locate the black boxes before those emitters, those pingers run out of batteries?

DAVID GALLO, CO-LED SEARCH FOR AIR FRANCE FLIGHT 447: Hi, Jim. It depends on an awful lot of things. I never put a lot of faith in

those pingers. You have to have almost perfect conditions, and the conditions here are far from perfect, especially since it's deep water. So, you know, I think they're better off looking for the wreck itself, scouring the sea floor with sonar and looking for the main body of the wreckage.

SCIUTTO: Thanks very much, Gallo -- Robert Gallo for helping us there.

We're going to leave this for a moment, because we're seeing more breaking thousand out of this protest outside this Trump rally. These are live pictures.

It appears the police have not been able to keep those two groups of protesters apart. That's been key. You have Trump supporters there, you have Trump protesters there. And when they get together, we have seen fists fly, we have seen bottles and rocks get thrown. And that's what you're seeing there right now.

I'm still here with my panel, Doug Heye, formerly with the RNC. As you look at this, is this damaging for the Republican Party?

HEYE: I think it is damaging for the Republican Party. One, these are ugly scenes and it is an event our nominally is holding. Two, something the entire country is seeing, and they're seeing always with this, some kind of racial or ethnic divide, it's something the party has been trying to heal for four years or longer.

[19:45:01] And we're just not able to do so, and these pictures like this really damage that.

SCIUTTO: Joe, how do you respond to that?

BORELLI: You know, the Trump rally itself has been over for quite a while and the people left are people only there to incite violence, to incite riots. It's a shame. It really is an embarrassment that this is what has devolved in political culture in America today.

But I've got to be honest. I see mostly not Trump supporters being ones engaging. And you look back at Albuquerque two nights ago. And you saw everything that happened there.

SCIUTTO: Sally?

KOHN: OK. First of all, we have a tradition of nonviolent protests to make political points in this country. And I applaud the protesters who are out there and hope they are all following in that great tradition.

We have seen throughout this election, Trump supporters engaging in violence, as well as violent rhetoric. But the larger issue here is the violence of Trump's policies.

You heard Homeland Security officials under George W. Bush, no peacenik, talk about the level of degrading, rounding up of people, of undocumented immigrants, raiding homes, raiding schools, raiding workplaces.

BORELLI: The Obama administration is --

(CROSSTALK)

KOHN: And how ugly it would be to round up and deport 11 million people. We're talking internment camps. Not my language, words that Bush administration officials used. So that is ugly that. That is violent. And these people, thank God, are protesting that as violating our history and our spirit, and, again, I applaud them.

SCIUTTO: Joe, do Trump's positions help fuel this kind of anger?

BORELLI: It -- look, a lot of people don't like Trump's positions. That's fine. That's their right.

Their right is also to protest. They can stand outside of a Trump rally. They can have signs saying the most hateful things and anything. It doesn't matter.

What matters is, taking that next step where you start assaulting police officers, you start assaulting people that are trying to leave a rally and it's wrong. And I think the Democratic candidates have to own it, and they have to say to their supporters to stop doing this.

SCIUTTO: Doug --

HEYE: I think there's blame all around.

And, again, politically, this is something that Republicans don't want to see. We have serious problems with Hispanics. The language that we have seen, at the time the front runner, now the nominee use, has been terrible for our outreach with Hispanics, with women. Pick your minority group. We've got big problems with them.

The only silver lining I see on this, when Trump staff says, well, they're not real positions, they're just suggestions. Gosh, we can only hope so.

SCIUTTO: Does this lose you the election?

HEYE: Potentially, yes. If we look at all of the polling we have seen, 85 percent of Hispanics disapprove of Trump, 73 percent of women. How do you win there? How do you win California?

SCIUTTO: Joe, how do you get over that?

BORELLI: I mean, since Trump won the nomination, we have seen one consistent thing. His number amongst independents has risen, meaning people are breaking towards him.

I think this doesn't do anything to help the anti-Trump movement. I think a lot of people see this as offensive, and they actually gravitate towards Donald Trump. They're sick of this.

SCIUTTO: Sally, do you buy that? KOHN: No, I don't. Again, you know, I think it was effective, and we

saw a period in time where people were protesting entering these events, and it was the reaction that they provoked. In these sort of violent stoked rhetorical environment of Trump rallies where then we saw his protesters respond in violence, and we heard him incite, encourage and say he would pay for the repercussions of that violence. So, that really for people crystallizes the kind of future, the kind of choice at stake in this election.

SCIUTTO: No question. Sally, Joe, Doug, thanks very much.

OUTFRONT next, on one of the busiest travel weekends of the year, our special report on America's outdated and overcrowded airports.

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[19:51:47] SCIUTTO: Breaking news. We continue to monitor these protests, three arrests there in San Diego outside a Donald Trump rally. We've seen it get heated, seen punches thrown, and as we said, there have been arrests by police there.

Looking forward as well, the security, as this weekend comes upon us, Memorial Day. Our nation's airports tested as millions of travelers look to get away this holiday weekend, one of the busiest travel days of the year.

The TSA, which is in desperate need of help, is struggling to keep those security lines moving, hasn't always worked.

So, how did the problem get so bad so fast?

Here's Rene Marsh has a story you'll only see here on OUTFRONT.

(BEGIN VIDEOTAPE)

RENE MARSH, CNN AVIATION CORRESONDENT (voice-over): Long lines.

UNIDENTIFIED FEMALE: We were insecurity for almost two hours.

MARSH: Missed flights.

UNIDENTIFIED MALE: Three and a half hours early, so it wasn't enough time.

MARSH: And frustrated passengers. It's become the standard at airports nationwide.

KEVIN BURKE, AIRPORT COUNCIL INTERNATIONAL: People going through airports built in the '50s, '60s, '70s. So, the airport structures can't accommodate.

MARSH: Decades ago when the airports were built, there were 62 million travelers. Today, that number has grown but capacity has not. More than 750 million passengers are expected to fly this year. Presidential candidates on both sides agree the nation's airports are not ready for the 21st century.

HILLARY CLINTON (D), PRESIDENTIAL CANDIDATE: I am tired that we don't have our country that's considered in the top 25.

TRUMP: You look at some of our airports, it's third world.

MARSH: Also in need of updating, the FAA's air traffic control system.

Doug Parker is the CEO of American Airlines.

DOUG PARKER, CEO, AMERICAN AIRLINES: Our flight times and what we schedule our times to be are longer than they would be if we had a more efficient air traffic control system.

MARSH: Airports like LaGuardia and LAX in Los Angeles have ranked as some of the country's worst in the past because of outdated terminals.

MARY GRADY, LOS ANGELES WORLD AIRPORTS: These terminals are old, kind of falling apart, and we really need to upgrade them, but that's difficult to do when you're constrained for space.

MARSH: Funding is finally coming through in some major cities, but at smaller airports like Kansas City which lacks amenities and space for passengers, they're still looking for the cash.

BURKE: We have new aircraft, for example, that are now flying in the United States, where gates don't accommodate an A380. Somebody has to pay for that.

MARSH: In the U.S., funding comes airlines, states, local municipalities and the federal government. But it is a simpler funding process in other parts of the world.

In South Korea, Incheon International consistently ranks as one of the best in the world. It's heavily funded by the government. There's entertainment, high end retail and computer stations, showers, spas, an on site hotel, full stage performances, and terminals are massive.

Congress regulates a tax at $4.50 on passenger air fare and $9 round trips.

[19:55:00] That money goes to airports for construction projects but the fee hasn't been raised to account for inflation in 16 years.

BURKE: It's not a fair fight. Their governments recognize the importance of airports, our government says it does, but they show it by increasing funding for us and looking at us as economic engine for local communities.

(END VIDEOTAPE)

SCIUTTO: So, Rene, which airports are most in need of an update upgrade? MARSH: Well, major airports like LaGuardia, and LAX, they are finally

starting to invest billions of dollars to renovate. But the problem is smaller and mid size airports that aren't hubs. They may not necessarily have the support of the airline, they may not have access to local money. They're still struggling with the old infrastructure they can't meet capacity not only for people but aircraft as well.

A lot of the airports have been pushing to increase that passenger tax, but the airlines don't like the idea, Jim, because it makes the ticket prices look a lot higher. Congress has the power to increase the tax but at this point, they have not.

SCIUTTO: Yes, that's tough to get through Congress.

Rene Marsh at Reagan National -- thanks very much.

And we'll be right back.

(COMMERCIAL BREAK)

SCIUTTO: You're looking live pictures of protesters outside Donald Trump's rally in San Diego. We're going to continue to monitor the crowd as police move in.